Somatosensory Systems Flashcards
What are the modalities of the somatosensory system?
Touch, proprioception, pain and visceral
What are the 4 physiological mechanisms of sensation?
Transduction, transmission, perception and modulation
What are the two classes of neurones that mediate somatic sensations?
dorsal root ganglion neurones
trigeminal sensory neurons
What do DRG’s and TSN’s do?
Transduce stimuli into electrical signals
transmit those signals to the CNS
What are the A-type of sensory receptors?
A-beta (touch) - large and lots of myelin
A-delta (temp,pain) - some myelin and different sizes
What are the 4 things receptors respond to?
modality
intensity
duration
location
The specificity of receptors?
Receptors are specialised to transduce a particular type of stimulus energy into electrical signals
What are SAR’s?
slowly adapting receptor - frequency of firing action potential increases with increasing intensity of stimulus
What are RAR’s?
rapidly adapting receptor - only fire when a change in intensity but stops when constant
What is the receptive field?
The receptive field of a sensory neuron is the spatial domain where stimulation excites or inhibits the neuron
What are the 4 types of mechanoreceptors?
Meissner corpuscle
Merkel cells
Pacinian corpuscle
Ruffini endings
What are the joint receptors?
Proprioceptors report on limb position
sensory receptors are in the joint
What are muscle receptors?
Main muscle fibres are sensitive to small changes in length
receptors around fusal fibres give information about length
Golgi tendons organs lie in series with the main muscle fibres and are sensitive to changes in muscle tension
What do thermoreceptors do?
They respond to warm or cold stimuli in the non-noxious range
cold sensitive fibres are myelinated A-delta axons
warm sensitive fibres are unmyelinated C axons
What are nociceptors?
They respond to damage or potentially damaging stimuli
